THE NITROGENOUS EXCRETION. URINE. 363 



From this point of view urea represents that part of the 

 original body nitrogen, aside from the creatine and nuclein 

 derivatives, which takes the normal course. It represents no 

 store of practically realizable energy, while with some of the 

 other bodies which escape in the urine this is not the case; 

 under more favorable conditions they might be expected to 

 suffer further oxidation with liberation of more heat. Such 

 ideal conditions are realized in some individuals more than 

 in others. 



Urea may be built up outside of the body by many syn- 

 thetic processes, but is most easily prepared by the conversion 

 of ammonium cyanate, NH 4 OCN, into the isomer. On evap- 

 oration of a solution of this salt the transformation into urea 

 is complete. Urea is very soluble in water, from which it 

 may be obtained easily in crystalline form. Its solutions are 

 easily decomposed by many oxidizing agents with formation 

 of water, carbon dioxide and free nitrogen, on which behavior 

 several of the processes for determining it are based. This 

 change is brought about by hypochlorites, for example, in this 



manner : 



CON 2 H 4 + 3 NaOCl = 3NaCl + 2H 2 O + CO 2 + N,. 



On the other hand, urea may take part in synthetic reactions 

 and may be combined to form complex substances, in certain 

 cases, as will be shown below. 



URIC ACID AND THE PURINE BODIES. 



Few topics in physiological chemistry have attracted more 

 attention than the relations of uric acid to other nitrogenous 

 products excreted in the urine, and its behavior in relation to 

 disease. The importance of the substance in this point of 

 view has undoubtedly been very frequently over-estimated and 

 even at the present time clinicians are much divided as to the 

 part it plays in certain diseases. This much may be said with 

 truth, however, that many of the fine spun theories which 

 have been advanced by medical men on the uric acid question, 



